Torque transfer device with hydrostatic torque control system

ABSTRACT

In one form, the present teachings provide a power transmission device that includes a rotatable input shaft, a rotatable output shaft and a ring gear fixed for rotation with the input shaft. A carrier is fixed for rotation with the output shaft. A pump assembly includes an inner rotor supported for rotation on the carrier and an outer rotor encompassing the inner rotor. The outer rotor is in driving meshed engagement with the ring gear. The pump provides pressurized fluid to one of first and second fluid ports. A flow restrictor is moveable to selectively restrict fluid flow relative to one of the first and second ports. 
     In another form, the present teachings provide a power transmission device with a ring gear and a carrier assembly that are coupled to first and second rotary members, respectively. The carrier assembly includes pump assemblies, each of which having a rotor pin, an inner rotor rotatably received on the rotor pin, and an outer rotor that is rotatably received over the inner rotor. The outer rotors have planet gear teeth that are meshingly engaged with teeth of the ring gear. First and second fluid conduits are coupled to first and second sides of the pump assemblies, respectively, to facilitate the flow of hydraulic fluid into and out of the pump assemblies when they are operated in a first rotational direction. A valve is coupled to at least one of the first and second fluid conduits. The valve has a valve element, which is movable between first and second positions, for controlling fluid flow through the valve.

BACKGROUND AND SUMMARY

The present disclosure relates generally to a power transmission deviceoperable to selectively transfer torque between first and second sets ofdrivable wheels of a vehicle. More particularly, the present disclosureis directed to a power transmission device with a hydrostatic torquecontrol system.

Due to increased demand for four-wheel drive vehicles, powertransmission systems are more frequently being incorporated into vehicledriveline applications for transferring drive torque to the wheels. Somevehicles include a power transmission device operably installed betweenthe primary and secondary drivelines. Such power transmission devicesare typically equipped with a torque transfer mechanism for selectivelytransferring drive torque from the primary driveline to the secondarydriveline to establish a four-wheel drive mode of operation. At leastone known torque transfer mechanism includes a dog-type lock-up clutchthat may be selectively engaged for rigidly coupling the secondarydriveline to the primary driveline when the vehicle is operated in thefour-wheel drive mode. When the lock-up clutch is released, drive torqueis delivered only to the primary driveline and the vehicle operates in atwo-wheel drive mode.

Another type of power transmission device, referred to as a transfercase, may be operable to automatically direct drive torque to thesecondary wheels without any input or action on the part of a vehicleoperator. When traction is lost at the primary wheels, a four-wheeldrive mode is entered. Some transfer cases are equipped with anelectrically-controlled clutch actuator operable to regulate the amountof drive torque transferred through a friction clutch to a secondaryoutput shaft. The actuator typically includes an electric motor toprovide an application force to the friction clutch.

While many power transfer devices are currently used in four-wheel drivevehicles, a need exists to advance the technology. For example,packaging concerns, weight and electrical power requirements of thepower transmission device may make such systems cost prohibitive in somefour-wheel drive applications.

A power transmission device with a ring gear and a carrier assembly thatare coupled to first and second rotary members, respectively. Thecarrier assembly includes pump assemblies, each of which having a rotorpin, an inner rotor rotatably received on the rotor pin, and an outerrotor that is rotatably received over the inner rotor. The outer rotorshave planet gear teeth that are meshingly engaged with teeth of the ringgear. First and second fluid conduits are coupled to first and secondsides of the pump assemblies, respectively, to facilitate the flow ofhydraulic fluid into and out of the pump assemblies when they areoperated in a first rotational direction. A valve is coupled to at leastone of the first and second fluid conduits. The valve has a valveelement, which is movable between first and second positions, forcontrolling fluid flow through the valve.

DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a schematic of a four-wheel drive vehicle equipped with apower transmission device of the present disclosure;

FIG. 2 is a perspective view of the power transmission device shown inFIG. 1; and

FIG. 3 is an exploded perspective view of the power transmission deviceshown in FIG. 2;

FIG. 4 is another exploded perspective view of the power transmissiondevice taken at a different angle; and

FIG. 5 is a cross-sectional side view of the power transmission deviceof the present disclosure.

DETAILED DESCRIPTION

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the disclosure,its application, or uses.

The present disclosure is directed to a power transmission device thatmay be adaptively controlled for modulating the torque transferredbetween a rotatable input member and a rotatable output member. Thetorque transfer mechanism may be useful within motor vehicle drivelinesand easily positioned at a variety of axial positions spaced apart froma driving axle assembly. Accordingly, while the present disclosure ishereinafter described in association with a specific structuralembodiment for use in a driveline application, it should be understoodthat the arrangement shown and described is merely intended toillustrate an exemplary use.

With reference to FIG. 1 of the drawings, a drive train 10 for afour-wheel vehicle is shown. Drive train 10 includes a first axleassembly 12, a second axle assembly 14 and a power transmission 16 fordelivering drive torque to the axle assemblies. In the particulararrangement shown, first axle assembly 12 is the front driveline whilesecond axle assembly 14 is the rear driveline. Power transmission 16includes an engine 18 and a multi-speed transmission 20 having anintegrated front differential unit 22 for driving front wheels 24 viaaxle shafts 26. A transfer unit or power take-off 28 is also driven bytransmission 20 for delivering torque to an input member 29 of acoupling 30 via a driveshaft 32. The input member 29 of the coupling 30is coupled to driveshaft 32 while its output member 33 is coupled to adrive component of a rear differential 34. Second axle assembly 14 alsoincludes a pair of rear wheels 38 connected to rear differential 34 viarear axle shafts 40.

Drive train 10 is shown to include an electronically-controlled powertransfer system 42 including coupling 30. Power transfer system 42 isoperable to selectively provide drive torque in a two-wheel drive modeor a four-wheel drive mode. In the two-wheel drive mode, torque is nottransferred via coupling 30. Accordingly, 100% of the drive torquedelivered by transmission 20 is provided to front wheels 24. In thefour-wheel drive mode, power is transferred through coupling 30 tosupply torque to rear wheels 38. The power transfer system 42 furtherincludes a controller 50 in communication with vehicle sensors 52 fordetecting dynamic and operational characteristics of the motor vehicle.The controller 50 is operable to control actuation of coupling 30 inresponse to signals from vehicle sensors 52. The controller 50 may beprogrammed with a predetermined target torque split between the firstand second sets of wheels. Alternatively, controller 50 may function todetermine the desired torque to be transferred through coupling 30 viaother methods. Regardless of the method used for determining themagnitude of torque to transfer, controller 50 operates coupling 30 tomaintain the desired torque magnitude.

An alternative power transfer system incorporates coupling 30 withoutthe use of controller 50. Control of coupling 30 may be accomplishedusing mechanical control devices as well. Accordingly, the control andfunction of coupling 30 may be accomplished without supply ofelectricity at all.

FIGS. 2-4 depict coupling 30 in greater detail. Coupling 30 ispositioned within a housing 54 (FIG. 1) containing a hydraulic fluid.Coupling 30 includes an input shaft 60 drivingly coupled to an outputshaft 62 by a planetary gear set 64. One end 66 of input shaft 60 mayinclude a coupling provision including an external spline for adriveline component such as driveshaft 32.

Planetary gear set 64 includes a ring gear 68 fixed for rotation withinput shaft 60. A plurality of pump assemblies 70 are rotatablysupported by a carrier assembly 72. Carrier assembly 72 is fixed forrotation with a flange 74 of output shaft 62. Carrier assembly 72includes a first plate 76 and a second plate 78 fixed to one another.Second plate 78 includes a central pin 80 extending through a centralaperture 82 formed in first plate 76. Central pin 80 extends beyondfirst plate 76 into a pocket 84 formed within input shaft 60. A bearing85 rotatably supports central pin 80 within pocket 84. A plurality ofrotor pins 86 axially extend from a sealing face 88 formed on secondplate 78. First plate 76 may be fixed to rotor pins 86 by fasteners (notshown) extending through apertures 87 formed in first plate 76.

Each pump assembly 70 is substantially similar to the other.Accordingly, only one will be described in greater detail. Each pumpassembly 70 is a gerotor-type pump having an inner rotor 90 and an outerrotor or pinion gear 92. Inner rotor 90 is rotatably supported on rotorpin 86. Inner rotor 90 includes a first face 94 and an opposing secondface 96. First face 94 is placed in very close proximity with orpossibly contacting a sealing face 98 of first plate 76. In similarfashion, second face 96 of inner rotor 90 is positioned in closeproximity with or possible engagement with sealing face 88 of secondplate 78. A plurality of lobes 100 are formed on an external surface ofinner rotor 90.

Outer rotor 92 also includes first and second faces 102, 104 positionedsubstantially along the same planes as first and second faces 94, 96 ofinner rotor 90, respectively. Outer rotor 92 includes a plurality ofinternal lobes 106 sized and shaped to receive lobes 100 of inner rotor90 to define a gerotor pump. A plurality of gear teeth 108 are formed onan external surface of outer rotor 92. A plurality of gear teeth 110formed on ring gear 68 are in meshed engagement with gear teeth 108 ofeach outer rotor 92.

Each rotor pin 86 is located at an eccentric axis relative to the axesof rotation of outer rotors 92. Guides 112 are partially positionedwithin grooves 114 formed on sealing face 88 to properly align outerrotors 92. Similarly, guides 116 are partially positioned within grooves118 formed on sealing face 98. The guides 112, 116 are received withingrooves 120, 122 formed on outer rotors 92 to accurately locate eachouter rotor 92 for rotation along an axis offset from an axis ofrotation of each inner rotor 90. Alternatively, guides 112 and 116 maybe integrally formed into outer rotor 92.

First plate 76 includes three sets of first and second arcuately shapedblind cavities 124, 126. Second plate 78 includes three sets of firstand second arcuately shaped through slots 128, 129. This arrangementdefines three sets of first fluid ports 130 defined by cavities 124 andslots 128 and second fluid ports 132 defined by cavities 126 and slots129. Based on a first direction of relative rotation between input shaft60 and output shaft 62, first fluid ports 130 are low pressure orsuction ports while second fluid ports 132 are high pressure or outputports of each pump assembly 70. When input shaft 60 is rotated relativeto output shaft 62 in an opposite direction, second fluid ports 132become the low pressure ports while first fluid ports 130 are the highpressure discharge ports.

Output shaft 62 includes a set of first passageways 134 in communicationwith first fluid ports 130 and a set of second passageways 136 incommunication with second fluid ports 132. First passageways 134partially extend through output shaft 62 from a first face 138 of outputshaft 62 to first output shaft ports 140. In similar fashion, secondpassageways 136 extend from first face 138 to second output shaft ports142. First output shaft ports 140 are formed at an axial locationextending a first distance A from first face 138. Second output shaftports 142 are positioned at a second distance B from first face 138.Distance B is greater than distance A.

A restrictor ring 150 circumscribes a substantially cylindrical portion152 of output shaft 62. Restrictor ring 150 is configured to axiallymove relative to an outer surface 154 of cylindrical portion 152.Restrictor ring 150 is further configured to completely restrict,partially restrict or not restrict flow of fluid entering or exitingeither of first and second passageways 134, 136. By controlling theaxial location of restrictor ring 150 relative to first output shaftports 140 and second output shaft ports 142, fluid flow within firstpassageways 134 and second passageways 136 may be controlled.Controlling the fluid flow through pump assemblies 70 controls amagnitude of torque transferred from input shaft 60 to output shaft 62.

The position of restrictor ring 150 may be controlled by controller 50and an actuation mechanism (not shown). Depending on the informationprovided from vehicle sensors 52, controller 50 may initiate a requestto transfer torque between input shaft 60 and output shaft 62.Alternatively, a vehicle user may directly make a torque transferrequest. Based on the magnitude of torque to be transferred, controller50 may cause the actuation mechanism to position restrictor ring 150 ata location partially restricting flow through either of first and secondpassageways 134, 136. Alternatively, flow through these passageways maybe completely restricted or not restricted at all. A spring 156 may bepositioned on cylindrical portion 152 of output shaft 62. Spring 156functions to bias restrictor ring 150 toward a position where flowthrough first passageway 134 and second passageway 136 is notrestricted. In this manner, a default mode of operating coupling 30includes transferring little or no torque between input shaft 60 andoutput shaft 62.

One skilled in the art will be appreciate that it is contemplated tocontrol the position of restrictor ring 150 by any number of methodsincluding a purely mechanical method without requiring electrical inputfrom a controller or an electric motor as well as other methodsincluding actuators operable by provision of electrical power, hydraulicpower or the like.

Furthermore, the foregoing discussion discloses and describes merelyexemplary embodiments of the present disclosure. One skilled in the artwill readily recognize from such discussion, and from the accompanyingdrawings and claims, that various changes, modifications and variationsmay be made therein without department from the spirit and scope of thedisclosure as defined in the following claims.

1. A power transmission device comprising: a rotatable input shaft; arotatable output shaft; a ring gear fixed for rotation with said inputshaft; a carrier fixed for rotation with said output shaft; a pumpassembly including an inner rotor supported for rotation on said carrierand an outer rotor encompassing said inner rotor, said outer rotor beingin driving meshed engagement with said ring gear, said pump providingpressurized fluid to one of first and second fluid ports; and a flowrestrictor moveable to selectively restrict fluid flow relative to oneof said first and second fluid ports.
 2. The power transmission deviceof claim 1 wherein said carrier is restricted from rotating relative tosaid ring gear when said flow restrictor restricts fluid flow.
 3. Thepower transmission device of claim 2 wherein said output shaft includesa first passageway terminating at said first fluid port and a secondpassageway terminating at said second fluid port.
 4. The powertransmission device of claim 3 wherein said first fluid port is locatedon an outer surface of a cylindrically shaped portion of said outputshaft.
 5. The power transmission device of claim 4 wherein said secondfluid port is located on said outer surface of said cylindrically shapedportion of said output shaft.
 6. The power transmission device of claim5 wherein said first fluid port is positioned at a first axial locationand said second fluid port is positioned at a second axial locationoffset from said first location.
 7. The power transmission device ofclaim 6 wherein said flow restrictor is shaped as a ring surrounding aportion of said output shaft and moveable between positions where saidfirst and second fluid ports are partially blocked, completely blockedand not blocked.
 8. The power transmission device of claim 7 whereinsaid flow restrictor is biased toward a position where fluid flow is notrestricted.
 9. The power transmission device of claim 1 wherein amagnitude of torque transferred between said input shaft and said outputshaft may be varied based on the position of said flow restrictor. 10.The power transmission of claim 9 further including a controller tocontrol the position of said flow restrictor based on vehicle conditionsand a request for torque transfer between said input shaft and saidoutput shaft.
 11. A power transmission device comprising: a first rotarymember; a second rotary member; a ring gear coupled to the first rotarymember for rotation therewith, the ring gear comprising a plurality ofring gear teeth; a carrier assembly coupled to the second rotary memberfor rotation therewith, the carrier assembly comprising a plurality ofpump assemblies, each of the pump assemblies comprising a rotor pin, aninner rotor rotatably received on the rotor pin, and an outer rotor thatis rotatably received over the inner rotor, each of the outer rotorshaving a plurality of planet gear teeth that are meshingly engaged withthe ring gear teeth; and a first fluid conduit coupled to a first sideof the pump assemblies and adapted to couple a suction side of the pumpassemblies to a supply of hydraulic fluid when the pump assemblies areoperated in a first rotational direction; a second fluid conduit coupledto a second side of the pump assemblies and adapted to receivepressurized fluid from the pump assemblies when the pump assemblies areoperated in the first rotational direction; and a valve coupled to atleast one of the first and second fluid conduits, the valve having avalve element for controlling fluid flow through the valve, the valveelement being movable between a first position and a second position.12. The power transmission device of claim 11 wherein the pumpassemblies comprise gerotor-type pumps.
 13. The power transmissiondevice of claim 11 wherein the valve element is concentric with arotational axis of the carrier assembly.
 14. The power transmissiondevice of claim 13 wherein the valve element is movable in an axialdirection that is parallel to the rotational axis.
 15. The powertransmission device of claim 13 wherein the valve comprises a spring forbiasing the valve element toward the first position.
 16. The powertransmission device of claim 15 wherein placement of the valve elementin the first position configures the valve such that the valve elementdoes not restrict fluid flow through the valve.
 17. The powertransmission device of claim 11 wherein the second fluid conduit is atleast partly formed in the second rotary member.
 18. The powertransmission device of claim 17 wherein the valve element is mounted onthe second rotary member.
 19. The power transmission device of claim 17wherein the carrier assembly comprises a plate member that abuts anaxial side of the inner rotors and the outer rotors, and wherein aportion of the second fluid conduit is formed in the plate member. 20.The power transmission device of claim 19 wherein the carrier assemblycomprises another plate that abuts an opposite axial side of the innerrotors and the outer rotors, and wherein a portion of the first fluidconduit is formed in the another plate member.
 21. The powertransmission device of claim 11 further comprising: a third fluidconduit coupled to the second side of the pump assemblies and adapted tocouple the suction side of the pump assemblies to the supply ofhydraulic fluid when the pump assemblies are operated in a secondrotational direction that is opposite the first rotational direction;and a fourth fluid conduit coupled to the first side of the pumpassemblies and adapted to receive pressurized fluid from the pumpassemblies when the pump assemblies are operated in the secondrotational direction.
 22. The power transmission device of claim 21wherein the valve is coupled to at least one of the third and fourthconduits.
 23. The power transmission device of claim 22 wherein thesecond and fourth fluid conduits include respective fluid ports in thesecond rotary member.